It turns out that 1 is now considered not to be a prime number, but up until the late 1800s it generally was. On the other hand, one stone can't be arranged in a "rectangular grid" as I described above. After all, 1 is only divisible by 1 and itself (which are the same thing!). So 8, 9 and 10 are not prime, but 11 is.įrom the definition/explanation above, you wouldn't be able to tell. Eight stones can be arranged in a 2×4 grid, nine stones in a 3×3 grid, ten stones in a 2×5 grid, but eleven stones cannot be arranged in a rectangular grid (a 1×11 grid doesn't count as "rectangular", otherwise this explanation would be pointless). A more intuitive way of grasping what a prime number is involves trying to arrange a number of stones (or beans, or whatever) into a rectangular grid. That's the definition usually taught in schools.
A prime number is a counting number which can't be divided, except by 1 or itself (every counting number can be divided by 1 and itself). Are prime numbers involved in any other areas of physics?įirst, we'll agree that by counting numbers we mean the familar positive whole numbers 1, 2, 3, 4, 5, 6.What's this about a link between prime numbers and quantum physics?.
What do we know about the gaps between consecutive primes numbers?.Do you get different prime numbers if you switch from base-10 to another base for representing numbers?.Why do people search for large prime numbers?.How are prime numbers used in cryptography?.Is it true that prime numbers have been used in attempts to communicate with extra-terrestrials?.Do prime numbers show up in the natural world?.Is there a pattern in the prime numbers?.Is there a formula for finding prime numbers?.2 is the only even prime number – why is that?.How can you tell if a number is prime or not?.Frequently asked questions about prime numbers: